At a legendary but secretive laboratory in California, Lockheed Martin is working on a plan that some employees hope might transform the world's energy system: a practicable type of nuclear fusion.
Some 900 miles to the north, Bill Gates and another Microsoft veteran, Nathan Myhrvold, have poured millions into a company developing a fission reactor that could run on today's nuclear waste.
And on the far side of the world, China has seized on discarded American research to pursue a safer reactor based on an abundant element called thorium.
Beyond the question of whether they will work, these ambitious schemes pose a larger issue: How much faith should we, as a society, put in the idea of a big technological fix to save the world from climate change?
A lot of smart people are coming to see the energy problem as the defining challenge of the 21st century. We have to supply power and transportation to an eventual population of 10 billion people who deserve decent lives, and we have to do it while limiting the emissions that threaten our collective future.
Yet we have already poured so much carbon dioxide, the main greenhouse gas, into the atmosphere that huge, threatening changes to the world's climate appear to be inevitable. And instead of slowing down, emissions are speeding up as billions of once-destitute people claw their way out of poverty, powered by fossil fuels.
Many environmentalists believe that wind and solar power can be scaled to meet the rising demand, especially if coupled with aggressive efforts to cut waste. But a lot of energy analysts have crunched the numbers and concluded that today's renewables, important as they are, cannot get us even halfway there.
"We need energy miracles," Gates said in a speech three years ago introducing his approach, embodied in a company called TerraPower.
A variety of new technologies might help. Bright young folks in American universities are working on better ways to store electricity, which could solve many of the problems associated with renewable power. Work has even begun on futuristic technologies that might cheaply pull carbon dioxide out of the air.
But because of the pressing need for thousands of large generating stations that emit no carbon dioxide while providing electricity day and night, many technologists keep returning to potential improvements in nuclear power.
After all, despite its many problems, it is the one low-carbon energy source that we know can work on a very large scale. France gets 80 percent of its electricity from nuclear reactors.
Perhaps Gates can find a way forward. He is the world's second-richest man and surely the premier American technologist of the era, following the death of Steve Jobs.
His partner in TerraPower is Myhrvold, the former chief technology officer at Microsoft. Adept in geophysics, space physics, mathematics, economics, paleontology and gastronomy, Myhrvold is the man behind a $600 cookbook called Modernist Cuisine and a slew of other wildly inventive projects.
Their plan is to build something called a traveling wave reactor. In principle, it could operate safely for a half-century or more without refueling and could run on material that has been discarded from today's reactors as hazardous waste, solving several problems at once.
They have persuaded an energy veteran, John Gilleland, to run the company; he employs about 60 people and is laying plans to build a prototype reactor.
"We sensed that nuclear had not been pushed in an innovative sense for some time," Gilleland said. "No one had taken 21st century technology and modeling capabilities and just sort of started over."
Their method, like that of existing reactors, is based on fission, or splitting heavy atoms, then using the resulting heat to spin turbines and make electricity.
Lockheed Martin is pursuing a more difficult course: fusion. It involves fusing hydrogen variants into heavier elements, similar to the reaction that powers the sun.
The company will not say much about the program under way at its legendary Skunk Works facility in California, which developed the U-2 spy plane. But in a videotaped speech this year, a leader of the program, Charles Chase, suggested it was aiming for small, modular fusion reactors that could be built in factories.
Among the new nuclear approaches, fission reactors based on thorium are especially intriguing, offering potentially huge safety advantages. The basic concepts were proved in research by the American nuclear establishment in the 1960s, but the idea was ultimately abandoned by the Nixon administration in favor of a riskier approach called breeder reactors, which turned into an $8 billion black hole.
An engineer in Alabama, Kirk Sorensen, has helped excavate the old thorium work and founded his own tiny company, Flibe Energy, to push it forward. But it will surprise no one to hear that China is ahead of the United States on this, with hundreds of engineers working on thorium reactors.
"They're doing laps around the track, and we haven't even decided if we're going to lace up our shoes," Sorensen said.
Yet not even the speedy Chinese are likely to get a sizable reactor built before the 2020s, and that is true for the other nuclear projects as well. So even if these technologies prove to work, it would not be surprising to see the time line for widespread deployment slip to the 2030s or the 2040s. And climate scientists tell us it would be folly to wait that long to start tackling the emissions problem.
Two approaches to the issue — spending money on the technologies we have now, or investing in future breakthroughs — are sometimes portrayed as conflicting. In reality, that is a false dichotomy. The smartest experts say we have to pursue both tracks at once, and much more aggressively than we have been doing.
An ambitious national climate policy, anchored by a stiff price on carbon dioxide emissions, would serve both goals at once. In the short run, it would hasten a trend of supplanting coal-burning power plants with natural gas plants, which emit less carbon dioxide. It would drive investment into current low-carbon technologies like wind and solar power that, while not efficient enough, are steadily improving.
And it would also raise the economic rewards for developing new technologies that could disrupt and displace the ones of today. These might be new-age nuclear reactors, vastly improved solar cells, or something entirely unforeseen.
In effect, our national policy now is to sit on our hands hoping for energy miracles, without doing much to call them forth. While we dawdle, maybe the Chinese will develop a nice business selling us thorium reactors based on our old designs. For communists, they do have an entrepreneurial bent.
But surely we would all feel better about the future if the full creative power of American capitalism were unleashed on the climate problem.